1. Field of the Invention
The invention relates to a clamping assembly for the attachment of an outer member, especially a hub with a cylindrical cavity, to a concentrically received, outwardly cylindrical inner member, especially a shaft, by means of a double-taper ring having one cylindrical peripheral surface and two oppositely slanting tapered peripheral surface portions, the maximum wall thickness of the ring being located axially in the mid-portion of the double-taper ring, the assembly including two cooperating tapered clamping sleeves with axially aligned cylindrical peripheral surfaces and oppositely tapered surfaces seated on the tapered surface portions of the double-taper ring, the assembly being clampable by means of axially oriented clamping bolts.
Tightening of the assembly by means of the clamping bolts causes the tapered clamping sleeves to engage the double-taper ring in a wedge action, thereby contracting the inner clamping element, while expanding the outer clamping element, or elements, as the case may be, and creating a clamping action between the cylindrical surface of the double-taper ring and either the shaft or the hub on the one hand, and between the cylindrical peripheral surfaces of the clamping sleeves and either the hub bore or the shaft, respectively, on the other hand, the clamping assembly creating considerable radial forces. The double-taper ring of this assembly may thus either constitute the outer clamping element with inwardly facing tapered surfaces, or the inner clamping element with outwardly facing tapered surfaces.
2. Description of the Prior Art
A clamping assembly of the general kind mentioned above is known from German Pat. No. 1,095,064. However, the double-taper ring disclosed therein consists of several separate rings. It takes the form of a thin-walled inner ring which cooperates with two thick-walled tapered outer clamping sleeves having axial bores for the clamping bolts, the latter being arranged radially outside the double-taper ring, reaching from one tapered clamping sleeve into the other.
The wedge action of this type of clamping assembly is primarily determined by the angle of taper of the tapered surfaces: a smaller angle of taper, i.e. a slimmer axial cone, creates a larger radial clamping force component, when the assembly is tightened. Accordingly, the radial preload and the maximum torque which can be transmitted with a given strength limit of the clamping bolts increases with a decreasing angle of taper.
The reduction of the taper angle on the tapered clamping surfaces finds a lower limit, however, where the axial displacement of the clamping sleeves under tightening of the clamping bolts requires excessive axial displacement of the former towards each other.
It has now been found that angles of taper which, under the above considerations, are still practical and which are desirable from the standpoint of obtaining a high torque-transmitting capability, fall within the range of self-locking engagement of the tapered surfaces. With the cooperating elements made of steel, this range begins at about 7.degree. of taper angle, measured between the tapered surface and the assembly axis. When the taper angle is chosen less than this value, the tapered surfaces lock themselves against each other so that, even after the clamping bolts are removed from the assembly, these surfaces reamin under clamping tension and cannot be disengaged freely, i.e. not without a forcible displacement of the clamping elements in the direction opposite to the clamping action of the clamping bolts.
If in the aforementioned prior art clamping assembly according to German Pat. No. 1,095,064, the tapered clamping surfaces have a taper angle lying within the range of self-locking tapers, then, the particular assembly cannot be disengaged. Even in the case where ring extracting screws are added, as in the case of the German Published Allowed Application (Auslegeschrift) No. 1,190,266, the latter are capable only of loosening one of the tapered clamping sleeves, namely the one which becomes loose first, while the other tapered clamping sleeves cannot be stripped from the double-taper ring, because there is no longer a counter-support for the stripping screws.